The present invention relates to an apparatus for detecting a particle agglutination pattern formed on an inclined bottom surface of a reaction vessel due to immunological agglutination reaction, and more particularly to an apparatus for determining various types of blood, existence of antigens and antibodies by detecting a blood corpuscular agglutination pattern formed on a conical bottom surface of a reaction vessel.
Various kinds of such detecting apparatuses have been proposed. In one of them, use is made of a reaction vessel made of transparent material and having a conical bottom surface. When an agglutination reaction proceeds in the reaction vessel, agglutinated particles are uniformly deposited on the inclined bottom surface just like as snow to form a uniformly deposited pattern. Contrary to this, when no agglutination reaction occurs, descending particles roll down along the inclined bottom surface and are collected at the lowermost central portion of the bottom to form a centrally collected pattern. Therefore, by detecting photoelectrically the particle pattern formed on the bottom surface, it is possible to known whether the agglutination reaction has occurred or not.
However, in the known apparatus, the reaction vessel is made of material having a refractive index different from that of the surrounding air and thus, the bottom wall serves as a kind of concave lens. Therefore, an image of the bottom surface formed on a light detector has not uniform brightness, but has greater brightness at its center than periphery. This results in that the particle agglutination pattern could not be accurately detected and sometimes erroneous judgement might be effected.